Where there is a database there are nerdy types who want to normalise it, formalise the ontology of it, rationalise it, enhance its performance and all the other things computer science bods and other nerds love to do. They do it because their training or their gut feel tells them it must be an improvement that everyone will welcome it. They are wrong.
If OSM didn't have a database, it would be easier to explain that we don't do that, and we don't want you to do that either. It would be easier to direct these meddling nuisances to some other project, maybe opendatabasewrangling or openstringuntangling. That way we could keep the freedom to carefully choose the tags we use without the risk that some prat would mass-edit them into his view of an organised world, losing all the detail and nuances carefully placed there by hundreds of other mappers. The really, really annoying thing is that most of these people don't actually consume the data in a useful way, it just seems like a good idea to them. If they did use the data they would quickly see that selecting the data you want with a little preprocessing is easy and you always have to do this, so adding some extras to cope with variety is fairly simple. Write the code once and it works over and over again.
Of course we need to store the data somewhere and in reality that needs to be a database, such as the one we have. I must make it clear that I'm not criticising the database, it's design or the way it is managed or run at all, just the fact that something called a database attracts unwelcome urges from a few people. Maybe we could just stop calling it a database. Can we rename it to the tag-pile, or the OSM toy-box or anything that doesn't convey 'database'?
I wish the people who want to reduce the tags to a proscribed list well - I just wish them well somewhere outside of OSM. If they want an organised, limited list of tags, take OSM data and play with it in their world as they want to - just don't upload the changes as a mass-edit back into our toy-box. There is real value in nuanced data and, more importantly, real value in not upsetting the mappers whose carefully chosen tags get squashed to homogenised blandness by these unthinking mass-editors.
What would you rename